While this is ok when you do new object assignments, it just bypass same instances of same object, since the hash is the same.
A user on IRC (post-o-matic) has a quite complex object logic that he would like to avoid clone and even instantiate another class.
I agree with him that cloning is not the ideal technique, mainly because the changeset would always compute the object (since then hashs would be different).

I was thinking in a possible alternative and it came up to me the same basic idea we have with operators overloading OR Comparable interface of Java. I know in Java it supports way more things, but at least for this situation (as a start point) it would make developer's life easier.

In this user's usecase, it'd require him to update the EffortGraph class and implement Comparable interface.
For his specific situation, he'd need to store original value and updated value, just like we do internally in UnitOfWork for Entities.

Guilherme Blanco
added a comment - 19/May/10 10:06 PM What's the final status of this?
IMHO this should be incorporated, since it adds a powerful support that users can take advantage in our Types.
Cheers,

Robert
added a comment - 04/Feb/11 3:16 AM +1 for this...
if you have datetimes in a table and are using the DateTime object, you end up with useless update queries, if you persist an unchanged object...

I have a simple object, that I save to the session. After merging it and flushing the entitiy manager, an update query is generated, which sets all the datetime fields of the object to their current value:

This code results in the expected SELECT query, which refreshes the item from DB, but it also results in an update query which sets the datetime of the object to the same value.
This query could be omitted, if I could use a comparable interface and a custom type for datetimes, which implement it.

Robert
added a comment - 04/Feb/11 4:35 AM - edited Sorry, I wasn't clear.
It does not happen in all cases.
I have a simple object, that I save to the session. After merging it and flushing the entitiy manager, an update query is generated, which sets all the datetime fields of the object to their current value:
Unable to find source-code formatter for language: php. Available languages are: actionscript, html, java, javascript, none, sql, xhtml, xml
$item = $_SESSION['item'];
$item = $ this ->_em->merge($item);
$ this ->_em->persist($item);
$ this ->_em->flush();
This code results in the expected SELECT query, which refreshes the item from DB, but it also results in an update query which sets the datetime of the object to the same value.
This query could be omitted, if I could use a comparable interface and a custom type for datetimes, which implement it.